Lambda Crucis

λ Crucis, Latinized as Lambda Crucis, is a single,^[10] variable star in the southern constellation Crux, near the constellation border with Centaurus. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude that fluctuates around 4.62.^[2] The star is located approximately 384 light-years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +12 km/s.^[5] It is a proper motion member of the Lower Centaurus–Crux sub-group in the Scorpius–Centaurus OB association, the nearest such association of co-moving massive stars to the Sun.^[6]

A light curve for Lambda Crucis, plotted from Hipparcos data^[11]

λ Crucis

Location of λ Crucis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Crux
Right ascension	12h 54m 39.18258s[1]
Declination	−59° 08′ 48.1229″[1]
Apparent magnitude (V)	4.62[2]
Characteristics
Evolutionary stage	main sequence
Spectral type	B4 Vne[3]
U−B color index	−0.60[4]
B−V color index	−0.15[4]
Variable type	β Cep?[2]
Astrometry
Radial velocity (Rv)	+12.0±4.2[5] km/s
Proper motion (μ)	RA: −32.92[1] mas/yr Dec.: −14.60[1] mas/yr
Parallax (π)	8.50±0.21 mas[1]
Distance	384 ± 9 ly (118 ± 3 pc)
Absolute magnitude (MV)	−1.2[6]
Details
Mass	5.0±0.1[7] M☉
Radius	3.00[8] R☉
Luminosity	790[6] L☉
Surface gravity (log g)	3.01[8] cgs
Temperature	16,500[8] K
Rotational velocity (v sin i)	290[8] km/s
Age	53.3±8.1[7] Myr
Other designations
λ Cru, Lambda Cru, CD−58°4794, HD 112078, HIP 63007, HR 4897, SAO 240368[9]
Database references
SIMBAD	data

λ Crucis is listed in the General Catalogue of Variable Stars as a possible β Cephei-type variable. Its brightness varies with an amplitude of 0^m.02 over a period of 0.3951 days.^[2] However, it is currently thought more likely to be a different type of variable,^[12] possibly a λ Eridani variable or rotating ellipsoidal variable.^[13][14]

This object is a B-type main-sequence star with a stellar classification of B4 Vne,^[3] where the suffix notation indicates "nebulous" (broad) lines due to rapid rotation, along with emission lines from circumstellar material, making it a Be star.^[13] It is around 53^[7] million years old and is spinning rapidly with a projected rotational velocity of 341 km/s.^[15] The star has five^[7] times the mass of the Sun and about 3.0^[8] times the Sun's radius. It is radiating 790^[6] times the luminosity of the Sun from its photosphere at an effective temperature of 16,500 K.^[8]